Existing fluorescent lamps are commonly made up of lamp tube 1, cathode 2, wire 3 and stem cap 5 as shown in FIG. 1. With this type of fluorescent lamp, one end of the wire connected to the cathode is fixed on the stem cap and the other end of the wire is led out from the lamp tube. As a result, the whole inner tube of the fluorescent lamp forms a discharge space, such that mercury-vapor pressure is commonly adjusted by partial tube wall at the coldest point; hence, its shortcomings include (1) relatively small adjustment range: it is impossible to have good effect if condition seriously departs from the norm; (2) difficult to make working state adjustment based on the intersectional effect between amalgam and tube wall at the coldest point for the fluorescent lamp using amalgam.